The present invention relates to optical recording media, such as optical discs and optical cards. The invention also relates to an optical recording/reproducing apparatus for performing optical recording and/or reproducing.
Because of recent rapid progress in the development in the field of information-processing technology, data is increasingly represented as digital signals. This is particularly the case in the fields of information processing, telecommunications, video display, and audio. There is therefore an increasing demand for high-density optical discs for recording information and distributing software. One of the most effective and reliable means being developed for providing such high-density optical discs involves the use of short wavelength blue laser beams for high numerical aperture (NA) optical systems to record and reproduce optical signals.
One example of such a high-density optical disc, is the digital versatile disc (DVD), which is becoming more standardized and used in practical applications. Technical developments for increasing the storage capacity of DVDs and media related to DVDs are reported in many publications, for example, "Nikkei Electronics", Vol. No. 688, May 5, 1997 (Table 1 on page 13).